Imlay S P, Argenyi Z B, Stone M S, McCollough M L, Henghold W B
Department of Pathology, University of Iowa Hospital and Clinics, Iowa City 52242, USA.
J Cutan Pathol. 1998 May;25(5):279-84. doi: 10.1111/j.1600-0560.1998.tb01734.x.
Parachordomas are rare cutaneous tumors that show virtually identical histologic findings to chordomas. Therefore, the major differential diagnosis in a case of parchordoma is metastatic chordoma. Parachordomas are benign neoplasms and most often develop on the extremities adjacent to tendons, synovium or osseous structures, as opposed to chordomas, which are malignant tumors located along the craniospinal axis. While recurrences may occur in cases of parachordoma, metastases have not been reported. In this report, two cases of parachordomas are reported and the literature reviewed. By light microscopy, parachordomas show eosinophilic bands of fibrous tissue separating lobules of cells with variably vacuolated cytoplasm (physaliphorous cells) admixed with more epithelioid cells in a myxoid stroma. Parachordomas and chordomas share immunohistochemical and ultrastructural features. Both stain with S-100 protein and vimentin, and ultrastructurally both demonstrate cytoplasmic vacuoles, intermediate filaments, pinocytotic vesicles, celljunctions, and cytoplasmic membranes with microvillous processes. Chordomas more frequently express cytokeratin (98% vs. 66% in parachordomas) and epithelial membrane antigen (90% vs. 20% in parachordomas) and chordomas have a larger number of rough endoplasmic reticulum-mitochondrial complexes. Thus, positive staining with epithelial membrane antigen and the identification of a large number of rough endoplasmic reticulum-mitochondrial complexes are suggestive of metastatic chordoma. However, the definitive distinction remains a clinical one after appropriate radiologic studies of the skull and spinal chord.
副脊索瘤是一种罕见的皮肤肿瘤，其组织学表现与脊索瘤几乎完全相同。因此，副脊索瘤病例的主要鉴别诊断是转移性脊索瘤。副脊索瘤是良性肿瘤，最常发生于与肌腱、滑膜或骨结构相邻的四肢，而脊索瘤是沿颅脊柱轴分布的恶性肿瘤。虽然副脊索瘤可能会复发，但尚未有转移的报道。在本报告中，报道了两例副脊索瘤病例并对相关文献进行了回顾。通过光学显微镜观察，副脊索瘤表现为纤维组织的嗜酸性带，将细胞小叶分隔开，细胞小叶内有不同程度空泡化的细胞质（泡状细胞），并在黏液样基质中混有较多的上皮样细胞。副脊索瘤和脊索瘤具有共同的免疫组化和超微结构特征。两者均对S-100蛋白和波形蛋白染色阳性，超微结构上均显示细胞质空泡、中间丝、吞饮小泡、细胞连接以及具有微绒毛突起的细胞质膜。脊索瘤更频繁地表达细胞角蛋白（98%，而副脊索瘤为66%）和上皮膜抗原（90%，而副脊索瘤为20%），并且脊索瘤有更多的粗面内质网-线粒体复合体。因此，上皮膜抗原阳性染色以及大量粗面内质网-线粒体复合体的发现提示为转移性脊索瘤。然而，在对头骨和脊髓进行适当的影像学检查后，最终的鉴别仍需基于临床情况。
